This invention relates to hydraulic steering limit valves for an auxiliary power steering system of a motor vehicle operative to shut off auxiliary power in the end deflection positions of the dirigible wheels of the vehicle.
Power steering limit valves are generally known and include a spring-loaded plunger operated by the steering shaft and continuously in fluid communication with pressure chambers of the servomotor and with a pressure operated valve in the end deflection positions of the dirigible wheels to form a short circuit between the servo pump supplying pressurized fluid to the steering circuit and the reservoir tank of the steering circuit. Simultaneously with the establishment of the short circuit by the plunger, fluid communication is established between the pressure operated valve and the corresponding pressure chamber of the servomotor to maintain it depressurized. Such a steering limit valve assembly is disclosed in U.S. Pat. No. 3,968,733, owned by the assignee of the present application.
The prior steering limit valve assembly aforementioned, is continuously under pressure to create a sealing problem since fluid leakage will result in functional failure. Further, application of prior steering limit valves to two or more steering circuits was not feasible because of costs.
It is therefore an important object of the present invention to provide a hydraulic steering limit valve assembly which will operate more reliably and also be suitable for several steering circuits.